As disclosed in JP-A-2005-127050, a vehicle may have a welcome function in which it is detected that a user has approached a vehicle, and a vehicle-mounted apparatus is operated to welcome the user to the vehicle. For example, the welcome function is realized by use of a keyless entry system or a passive entry system.
Specifically, a vehicle-mounted transmitter mounted in the vehicle intermittently transmits a response request signal at predetermined intervals. When a user carrying a portable device approaches the vehicle, the portable device receives the response request signal, and responds with a response signal. When the vehicle-mounted transmitter mounted in the vehicle receives the response signal, for example, a welcome light provided in a side view mirror is turned on to illuminate the ground in the vicinity of a door, and welcomes the user to the vehicle.
The transmission of a response request signal from the vehicle-mounted transmitter is performed by a rolling method. For this reason, when the amount of stop time of an engine of the vehicle is increased, and the vehicle-mounted transmitter intermittently transmits a response request signal, electrical power is continuously consumed, and a battery of the vehicle, which is a power supply, is discharged, which is a problem.
In the system disclosed in JP-A-2001-98810, when the voltage of a battery is decreased to be lower than the voltage required to guarantee the driving of a door lock mechanism, the transmission of a response request signal from a vehicle-mounted transmitter is stopped. In the system disclosed in JP-A-10-297430, when an occupant sensor detects an occupant, the transmission of a response request signal from a vehicle-mounted transmitter is stopped. In the systems disclosed in JP-A-2001-98810 and JP-A-10-297430, when a portable device or a function stop switch provided in a vehicle is operated, the transmission of a response request signal from a vehicle-mounted transmitter is stopped. In the systems disclosed in JP-A-10-297430 and JP-A-2012-36669, a time slot, for which the transmission of a response request signal from a vehicle-mounted transmitter is stopped, is set.
In the system disclosed in JP-A-2008-38514, vehicle-mounted transmitters are respectively provided on the outsides of seats of a vehicle, and response request signals are transmitted according to an intermittent output control pattern in which the amount of time, for which two or more (but less than the total number of vehicle-mounted transmitters) of the vehicle-mounted transmitters transmit response request signals at the same time, is determined.